Container

Abstract

To provide a container that is designed to prevent the fibrillation of polytetrafluoroethylene.SOLUTION: A container for filling polytetrafluoroethylene is cylindrical with a forward or inverse tapered inner side wall.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a container for filling polytetrafluoroethylene.

Background Art

[0002] Patent Documents 1 and 2 describe the use of an aqueous dispersion of polytetrafluoroethylene as a binder for a battery.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present disclosure is to provide a container in which fibrillation of polytetrafluoroethylene hardly occurs.

Means for Solving the Problems

[0005] The present disclosure (1) is a container for filling polytetrafluoroethylene, and the inner wall of the side surface is a cylindrical shape with a forward taper or a reverse taper.

[0006] The present disclosure (2) is the container according to the present disclosure (1), wherein the polytetrafluoroethylene has an extrusion pressure of 5 MPa or more at a reduction ratio of 100 and / or is stretchable.

[0007] The present disclosure (3) is the container according to the present disclosure (1) or (2), wherein the polytetrafluoroethylene has an extrusion pressure of 5 MPa or more at a reduction ratio of 100 and is stretchable.

[0008] The present disclosure (4) is the container according to any one of the present disclosures (1) to (3), wherein the extrusion pressure at the reduction ratio of 100 of the polytetrafluoroethylene is 5 to 20 MPa.

[0009] The present disclosure (5) is the container according to any one of the present disclosures (1) to (4), wherein the polytetrafluoroethylene is used as a binder for an electrochemical device.

[0010] The present disclosure (6) is the container according to any one of the present disclosures (1) to (5), wherein the difference between the inner diameter of the upper surface and the inner diameter of the lower surface is 5 to 100 mm.

[0011] The present disclosure (7) is the container according to any one of the present disclosures (1) to (6), wherein the taper angle is 0.5 to 10°.

[0012] The present disclosure (8) is the container according to any one of the present disclosures (1) to (7), wherein the material is polypropylene substantially free of a plasticizer.

[0013] The present disclosure (9) is the container according to any one of the present disclosures (1) to (8), wherein the surface roughness of the inner wall is 1.00 μm or less.

[0014] The present disclosure (10) is the container according to any one of the present disclosures (1) to (9), comprising a main body having an opening, a lid attached to the opening, and a clamp for fixing the lid.

[0015] The present disclosure (11) is the container according to the present disclosure (10), wherein the lid is attached to the opening in a state where a step provided on the lid and a protrusion provided on the main body are engaged, and / or a protrusion provided on the lid and a step provided on the main body are engaged.

[0016] The present disclosure (12) is the container according to any one of the present disclosures (1) to (11), wherein the water content of the polytetrafluoroethylene is 0.050 mass% or less.

[0017] The disclosure (13) is the container according to any one of disclosures (1) to (12) wherein the apparent density of the polytetrafluoroethylene is 0.40 to 0.60 g / ml.

[0018] The disclosure (14) is the container according to any one of disclosures (1) to (13) wherein the apparent density of the polytetrafluoroethylene is 0.43 to 0.60 g / ml.

[0019] The disclosure (15) is the container according to any one of disclosures (1) to (14) wherein the powder particle size of the polytetrafluoroethylene is 300 to 700 μm.

[0020] The disclosure (16) is the container according to any one of disclosures (1) to (15) wherein the powder particle size of the polytetrafluoroethylene is 500 to 700 μm.

[0021] The disclosure (17) is the container according to any one of disclosures (1) to (16) wherein the standard specific gravity of the polytetrafluoroethylene is 2.200 or less.

[0022] The disclosure (18) is the container according to any one of disclosures (1) to (17) wherein the standard specific gravity of the polytetrafluoroethylene is 2.130 to 2.170.

[0023] The disclosure (19) is the container according to any one of disclosures (1) to (18) wherein the apparent density of the polytetrafluoroethylene is 0.43 to 0.60 g / ml, the powder particle size is 500 to 700 μm, and the standard specific gravity is 2.130 to 2.170.

[0024] The disclosure (20) is the container according to any one of disclosures (1) to (19) wherein the polytetrafluoroethylene is a homopolymer of tetrafluoroethylene or a modified polytetrafluoroethylene containing a polymerization unit based on tetrafluoroethylene and a polymerization unit based on a modified monomer.

[0025] The present disclosure (21) is the container according to the present disclosure (20), wherein the modified monomer is at least one selected from the group consisting of perfluoro (methyl vinyl ether) and hexafluoropropylene.

[0026] The present disclosure (22) is the container according to any one of the present disclosures (1) to (21), filled with the polytetrafluoroethylene.

[0027] The present disclosure (23) is the container according to any one of the present disclosures (1) to (22), wherein the container is provided with a moisture absorbent.

[0028] The present disclosure (24) is a method for storing polytetrafluoroethylene, wherein the container according to any one of the present disclosures (1) to (23) is filled with the polytetrafluoroethylene and stored.

[0029] The present disclosure (25) is a container for filling polytetrafluoroethylene, wherein the mass of the polytetrafluoroethylene to be filled is 10 kg or less.

[0030] The present disclosure (26) is the container according to the present disclosure (25), wherein the mass of the polytetrafluoroethylene to be filled is 5 kg or less.

[0031] The present disclosure (27) is the container according to the present disclosure (25) or (26), wherein the powder particle size of the polytetrafluoroethylene is 100 μm or more and less than 600 μm.

[0032] The present disclosure (28) is the container according to any one of the present disclosures (25) to (27), wherein the apparent density of the polytetrafluoroethylene is 0.35 to 0.48 g / ml.

[0033] The present disclosure (29) is the container according to any one of the present disclosures (25) to (28), wherein the moisture content of the polytetrafluoroethylene is 0.050% by mass or less.

[0034] The disclosure (30) is a container according to any one of disclosures (25) to (29) in which the water content of the polytetrafluoroethylene is 0.005% by mass or less.

[0035] The disclosure (31) is a container according to any one of disclosures (25) to (30) in which the standard specific gravity of the polytetrafluoroethylene is 2.130 to 2.170.

[0036] The disclosure (32) is a container according to any one of disclosures (25) to (31) in which the water content of the polytetrafluoroethylene is 0.005% by mass or less, the apparent density is 0.35 to 0.48 g / ml, the powder particle size is 100 μm or more and less than 600 μm, and the standard specific gravity is 2.130 to 2.170.

[0037] The disclosure (33) is a container according to any one of disclosures (25) to (32) in which the polytetrafluoroethylene has a powder particle size of 100 μm or more and less than 300 μm and / or an apparent density of 0.35 g / ml or more and less than 0.40 g / ml.

[0038] The disclosure (34) is a container according to any one of disclosures (25) to (33) filled with the polytetrafluoroethylene.

Advantages of the Invention

[0039] According to the present disclosure, it is possible to provide a container in which fibrillation of polytetrafluoroethylene is less likely to occur.

Brief Description of the Drawings

[0040]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Mode for Carrying Out the Invention

[0041] When the present inventors studied polytetrafluoroethylene, it was found that polytetrafluoroethylene, which is useful as a binder for electrochemical devices such as batteries, tends to fibrillate more easily than ordinary polytetrafluoroethylene when stored or transported in a filled state. In applications where a large amount of polytetrafluoroethylene is used, even if a part fibrillates, there is no major problem. However, when used as a binder for electrochemical devices, the amount used is small and the influence of fibrillation is large, so strong suppression of fibrillation is strongly required.

[0042] As a result of further studies by the present inventors, it was found that if the inner wall of the side surface is a cylindrical container with a forward taper or a reverse taper, fibrillation of the filled polytetrafluoroethylene is suppressed, leading to the first present disclosure. In addition, the present inventors found that by setting the mass of the polytetrafluoroethylene filled in the container to 10 kg or less, fibrillation of the filled polytetrafluoroethylene is suppressed, leading to the second present disclosure.

[0043] Hereinafter, the present disclosure will be specifically described.

[0044] The first present disclosure is a container for filling polytetrafluoroethylene, and the inner wall of the side surface is a cylindrical shape with a forward taper or a reverse taper.

[0045] When the container is filled with polytetrafluoroethylene (PTFE), the PTFE powder (particles) is crushed by its own weight and becomes hard by being compacted. Usually, the PTFE powder needs to be loosened before use, but fibrillation is considered to occur when loosening such hardened powder. The container of the first disclosure makes the inner wall of the side surface a forward taper or a reverse taper, so that the force generated by its own weight is less likely to be applied to the PTFE powder and it is less likely to be compacted, thus suppressing fibrillation.

[0046] In the container of the first disclosure, the mass of the PTFE to be filled is preferably 30 kg or less, more preferably 20 kg or less, still more preferably 15 kg or less. The lower limit is not particularly limited, but is usually 1 kg or more.

[0047] The internal volume of the container of the first disclosure has an upper limit of preferably 150 L or less, more preferably 120 L or less, still more preferably 100 L or less, and even more preferably 80 L or less. The lower limit is not particularly limited, but is preferably 5 L or more, more preferably 10 L or more, and still more preferably 20 L.

[0048] Hereinafter, an example of the container of the first disclosure will be described with reference to the drawings.

[0049] As shown in FIG. 1, the container 1 includes a main body 2, a lid 3, and a clamp 4.

[0050] The main body 2 is a columnar member with the inner wall 2a and the outer wall 2b of the side surface being forward tapered, and PTFE is filled from the opening 2c on the upper surface. After filling the PTFE, the lid 3 is attached to the opening 2c of the main body 2, and the lid 3 is fixed by the clamp 4, so that the inside of the main body 2 is sealed.

[0051] The lid 3 is a circular member configured to cover the opening 2c and the side surface of the main body 2. As shown in Fig. 2, a stepped portion 3a is provided at the portion in contact with the outer wall 2b inside the lid 3, and a protrusion 2d is provided outside the opening 2c of the main body 2. The lid 3 is attached to the opening 2c in a state where the stepped portion 3a and the protrusion 2d are engaged with each other. Thereby, the sealing property inside the main body 2 is improved.

[0052] The clamp 4 is a ring-shaped member for fixing the lid 3 to the main body 2. As shown in Fig. 3, the clamp 4 is in an open-ring state before attachment, and after attachment, it is closed by the attachment portion 4a and tightened to fix the lid 3 to the main body 2. Thereby, the sealing property inside the main body 2 is improved.

[0053] PTFE used as a binder for an electrochemical device is required to have a low water content. Since the container 1 has a very high sealing property inside the main body 2 due to the above-described configuration, PTFE can be stored in a state with a low water content.

[0054] The difference between the inner diameter of the upper surface and the inner diameter of the lower surface of the main body 2 is preferably 5 mm or more, more preferably 10 mm or more, still more preferably 15 mm or more, particularly preferably 20 mm or more, and preferably 100 mm or less, more preferably 80 mm or less, still more preferably 60 mm or less, and particularly preferably 50 mm or less. The above-mentioned inner diameter of the upper surface is preferably 250 mm or more, more preferably 300 mm or more, still more preferably 350 mm or more, particularly preferably 400 mm or more, and preferably 800 mm or less, more preferably 700 mm or less, and still more preferably 600 mm or less. The inner diameter of the lower surface is preferably 200 mm or more, more preferably 250 mm or more, still more preferably 300 mm or more, particularly preferably 350 mm or more, and preferably 750 mm or less, more preferably 650 mm or less, still more preferably 600 mm or less, particularly preferably 550 mm or less.

[0055] The taper angle of the inner wall 2a is preferably 0.5° or more, more preferably 1° or more, still more preferably 1.5° or more, particularly preferably 2° or more, and preferably 10° or less, more preferably 9° or less, still more preferably 8° or less, even more preferably 7° or less, even more preferably 6° or less, particularly preferably 5° or less. The preferred range of the taper angle of the outer wall 2b is the same as that of the inner wall 2a. The above taper angle means the inclination angle of the wall surface with respect to the normal (see "taper angle A" in Fig. 1).

[0056] The taper ratio of the container 1 is preferably 0.01 or more, more preferably 0.02 or more, still more preferably 0.03 or more, even more preferably 0.04 or more, particularly preferably 0.05 or more, and preferably 0.20 or less, more preferably 0.19 or less, still more preferably 0.18 or less, even more preferably 0.17 or less, even more preferably 0.16 or less, particularly preferably 0.15 or less. The above taper ratio is a value defined by |upper surface inner diameter of the main body 2 - lower surface inner diameter of the main body 2| / height of the main body 2.

[0057] The height of the main body 2 is preferably 200 mm or more, more preferably 250 mm or more, still more preferably 300 mm or more, and preferably 500 mm or less, more preferably 450 mm or less, still more preferably 400 mm or less.

[0058] The material of container 1 (especially the main body 2 and the lid 3 that come into contact with PTFE) is preferably polypropylene that substantially does not contain a plasticizer. Thereby, the mixing of impurities into PTFE is suppressed. Substantially not containing a plasticizer means that the content of the plasticizer in polypropylene is 1.0% by mass or less.

[0059] The surface roughness of the inner wall 2a is preferably 1.00 μm or less. Thereby, fibrillation of PTFE due to contact with the inner wall 2a is suppressed. The lower limit is not particularly limited, but is usually about 0.20 μm. The above surface roughness is obtained by observing the surface at a magnification of 5 times using a shape analysis laser microscope VK-X1000 series manufactured by Keyence Corporation to obtain an observation image, and measuring the arithmetic mean roughness at a distance of 2.5 mm for the obtained image using the analysis application attached to the apparatus. Similarly, a total of three images are taken and the arithmetic mean roughness is measured, and it is a value calculated as the average value thereof.

[0060] Note that the container of the first disclosure is not limited to the above-described form, and other forms may be used. For example, as shown in FIG. 4, the inner wall 2a and the outer wall 2b on the side surface may be reverse tapered. Also, as shown in FIG. 5, the inner wall 2a on the side surface may be forward tapered and the outer wall 2b may have a shape that is not tapered (linear along the normal). Also, as shown in FIG. 6, in a form opposite to FIG. 2, that is, a protrusion 3b is provided at a portion in contact with the outer wall 2b inside the lid 3, and a stepped step 2e is provided outside the opening 2c of the main body 2. The lid 3 may be attached to the opening 2c in a state where the protrusion 3b and the step 2e are engaged with each other.

[0061] The second disclosure is a container for filling polytetrafluoroethylene, and is a container in which the mass of the polytetrafluoroethylene to be filled is 10 kg or less.

[0062] Since the mass of the PTFE filled in the second disclosed container is 10 kg or less, the force generated by its own weight is less likely to be applied to the PTFE powder, making it difficult to be compacted, so fibrillation can be suppressed. Also, it is preferable to fill the second disclosed container with PTFE powder having a low apparent density. Thereby, the force generated by its own weight is less likely to be applied to the PTFE powder, making it difficult to be compacted, so fibrillation can be suppressed.

[0063] In the second disclosed container, the mass of the PTFE to be filled is preferably 8 kg or less, more preferably 6 kg or less, still more preferably 5 kg or less. The lower limit is not particularly limited, but is usually 1 kg or more.

[0064] The internal volume of the second disclosed container has an upper limit that is preferably 75 L or less, more preferably 60 L or less, still more preferably 50 L or less, and even more preferably 40 L or less. The lower limit is not particularly limited, but is preferably 5 L or more, more preferably 10 L or more.

[0065] The second disclosed container may have a cylindrical shape with a forward taper or a reverse taper on the inner wall of the side surface, or may have a cylindrical shape with a non-tapered shape (linear along the normal) on the inner wall of the side surface. In terms of being able to suppress fibrillation, it is preferable that the inner wall of the side surface has a cylindrical shape with a forward taper or a reverse taper. Examples of the container with a cylindrical shape with a forward taper or a reverse taper on the inner wall of the side surface include the same forms as the first disclosed container (the forms in FIGS. 1 to 6). Examples of the container with a cylindrical shape with a non-tapered shape (linear along the normal) on the inner wall of the side surface include the form shown in FIG. 7.

[0066] Hereinafter, the first and second disclosed containers are collectively referred to as the disclosed container of the present disclosure.

[0067] The container of the present disclosure may be filled with a moisture absorbent to maintain a dry state inside the container. Specific examples of the moisture absorbent include silica gel, calcium oxide, calcium chloride, etc. Silica gel and calcium oxide are preferred, and silica gel is more preferred. The moisture absorbent may be granular or sheet-like. Further, it may be used by being put in a packaging material, or may be used in an exposed state. Further, it may be disposed on the PTFE filled in the container, or may be disposed at an installation location provided on the inner surface of the container such as the back surface of the lid.

[0068] When using a conventional container, it was necessary to store it at a low temperature (5 to 20 ° C) to suppress fibrillation. However, in the container of the present disclosure, fibrillation hardly occurs even at room temperature. Therefore, depending on the region and time, PTFE can be stored without temperature control, and there is also an advantage that the burden during storage is small. The present disclosure also relates to a storage method of storing PTFE in the container of the present disclosure. In the storage method of the present disclosure, PTFE can be stored at room temperature (15 to 30 ° C (preferably 25 to 30 ° C)).

[0069] Hereinafter, the PTFE filled in the container of the present disclosure will be described.

[0070] The above PTFE can be suitably used as a binder for an electrochemical device. Examples of the electrochemical device include a lithium ion secondary battery, a lithium ion capacitor, a capacitor (hybrid capacitor, electric double layer capacitor), a radical battery, a solar battery (particularly a dye-sensitized solar battery), a lithium ion primary battery, a fuel cell, various electrochemical sensors, an electrochromic element, an electrochemical switching element, an aluminum electrolytic capacitor, a tantalum electrolytic capacitor, etc. The binder may be an electrode binder or a solid electrolyte binder.

[0071] When the above PTFE is used as a binder for an electrochemical device, the above PTFE may be used alone, or may be used in mixture with other materials (for example, polymers other than PTFE).

[0072] The form of the above PTFE is preferably powder.

[0073] The above PTFE is useful as a binder for electrochemical devices such as batteries. Since fibrillation is likely to occur and the present disclosure is particularly effective, the extrusion pressure at a reduction ratio (RR) of 100 is preferably 5 MPa or more, and / or it is preferably stretchable. More preferably, the extrusion pressure at RR100 is 5 MPa or more and it is stretchable.

[0074] The above PTFE preferably has an extrusion pressure at a reduction ratio (RR) of 100 of 5 MPa or more. In terms of improving handleability, adhesive strength, and flexibility of electrodes, etc., it is more preferably 10 MPa or more, still more preferably 12 MPa or more, even more preferably 13 MPa or more, and particularly preferably 15 MPa or more. The extrusion pressure at RR100 is preferably 50 MPa or less, more preferably 40 MPa or less, still more preferably 35 MPa or less, even more preferably 30 MPa or less, even more preferably 25 MPa or less, and particularly preferably 20 MPa or less in terms of improving processability.

[0075] The above PTFE preferably has an extrusion pressure at RR300 of 10 Pa or more, more preferably 15 MPa or more, still more preferably 20 MPa or more, even more preferably 25 MPa or more, and particularly preferably 30 MPa or more in terms of improving handleability, adhesive strength, and flexibility of electrodes, etc. The extrusion pressure at RR300 is preferably 45 MPa or less, more preferably 40 MPa or less in terms of improving processability.

[0076] The extrusion pressure at RR100 is measured by the following method. Mix 50 g of PTFE powder and 10.25 g of hydrocarbon oil (trade name: Isopar E, manufactured by ExxonMobil) as an extrusion aid in a polyethylene container for 3 minutes. At room temperature (25 ± 2 °C), fill the cylinder of the extruder with the above mixture, apply a load of 0.47 MPa to the piston inserted into the cylinder, and hold for 1 minute. Next, extrude from the orifice at a ram speed of 18 mm / min. The ratio of the cross-sectional area of the cylinder to the cross-sectional area of the orifice (reduction ratio) is 100. In the latter half of the extrusion operation, the value obtained by dividing the load (N) when the pressure reaches an equilibrium state by the cross-sectional area of the cylinder is defined as the extrusion pressure (MPa).

[0077] The extrusion pressure in RR300 is measured by the following method. Mix 50 g of PTFE powder and 11.00 g of hydrocarbon oil (trade name: Isopar E, manufactured by ExxonMobil) as an extrusion aid in a polyethylene container for 3 minutes. At room temperature (25 ± 2 °C), fill the cylinder of the extruder with the above mixture, apply a load of 0.47 MPa to the piston inserted into the cylinder, and hold for 1 minute. Next, extrude from the orifice at a ram speed of 18 mm / min. The ratio of the cross-sectional area of the cylinder to the cross-sectional area of the orifice (reduction ratio) is 300. In the latter half of the extrusion operation, the value obtained by dividing the load (N) when the pressure reaches an equilibrium state by the cross-sectional area of the cylinder is defined as the extrusion pressure (MPa).

[0078] The above PTFE may or may not be stretchable, but it is preferably stretchable. Being stretchable means that a stretched body can be obtained in the following stretching test. Dry the beads obtained by paste extrusion in RR100 at 230 °C for 30 minutes to remove the lubricant. Cut the dried beads to an appropriate length, place them in a furnace heated to 300 °C, and stretch them in the furnace at a stretching speed of 1000% / second.

[0079] The above PTFE is preferably stretchable 25 times in terms of improving handling properties, adhesion, and flexibility of electrodes and the like. Whether it can be stretched 25 times can be confirmed by the following stretching test. The bead obtained by paste extrusion with the above RR100 is dried at 230 °C for 30 minutes to remove the lubricant. The dried bead is cut to an appropriate length and placed in a furnace heated to 300 °C. In the furnace, it is stretched at a stretching rate of 1000% / second until it reaches 25 times the bead length before the stretching test. If it does not break during stretching, it is determined that it can be stretched 25 times.

[0080] The above PTFE preferably contains substantially no moisture. This is advantageous in the production process because a wide range of electrode active materials can be selected for combination. Substantially free of moisture means that the moisture content in the above PTFE is 0.050% by mass or less. The above moisture content is preferably 0.040% by mass or less, more preferably 0.020% by mass or less, still more preferably 0.010% by mass or less, even more preferably 0.005% by mass or less, and particularly preferably 0.002% by mass or less. The above moisture content is measured by the following method. Measure the mass of the PTFE powder before and after heating at 150 °C for 2 hours, and calculate according to the following formula. Take the sample three times, calculate each time, then find the average and adopt the average value. Moisture content (% by mass) = [(mass of PTFE powder before heating (g)) - (mass of PTFE powder after heating (g))] / (mass of PTFE powder before heating (g)) × 100

[0081] The above PTFE preferably has an apparent density of 0.40 g / ml or more, more preferably 0.43 g / ml or more, still more preferably 0.45 g / ml or more, and even more preferably 0.48 g / ml or more in terms of improved handleability. The upper limit is not particularly limited, and it may be 0.60 g / ml. The above apparent density is measured in accordance with JIS K 6892.

[0082] The above PTFE preferably has an apparent density of less than 0.50 g / ml, more preferably 0.48 g / ml or less, still more preferably 0.45 g / ml or less, even more preferably 0.40 g / ml or less, particularly preferably less than 0.40 g / ml in terms of suppressing fibrillation. Also, it preferably has an apparent density of 0.20 g / ml or more, more preferably 0.25 g / ml or more, still more preferably 0.30 g / ml or more, and particularly preferably 0.35 g / ml or more.

[0083] The above PTFE preferably has a powder particle size of 300 μm or more, more preferably 450 μm or more, still more preferably 500 μm or more, even more preferably 550 μm or more, particularly preferably 600 μm or more in terms of improving handleability. Also, it preferably has a powder particle size of 1000 μm or less, more preferably 900 μm or less, still more preferably 800 μm or less, and particularly preferably 700 μm or less. The above powder particle size is determined by the laser diffraction method. It is carried out dry using a HELOS&ROD OS system (trade name, manufactured by SYMPATEC). The particle size distribution of the powder to be measured dispersed by compressed air with a dispersion pressure of 2 bar is calculated by measuring the shadow of the powder to be measured projected by a laser with a measurement sensor unit, and the value of the average particle diameter (50% integrated particle diameter) d50 on a volume basis is obtained for measurement.

[0084] The above PTFE preferably has a powder particle size of less than 600 μm, more preferably 400 μm or less, still more preferably 300 μm or less, particularly preferably less than 300 μm in terms of suppressing fibrillation. Also, it preferably has a powder particle size of 10 μm or more, more preferably 50 μm or more, and particularly preferably 100 μm or more.

[0085] The above PTFE preferably has a standard specific gravity (SSG) of 2.200 or less, more preferably 2.180 or less, still more preferably 2.170 or less, even more preferably 2.160 or less, even more preferably 2.150 or less, and even more preferably 2.145 or less, in terms of improved handleability, stretchability, adhesiveness, and flexibility of electrodes and the like. The above SSG is preferably 2.130 or more. The above SSG is measured by the water displacement method in accordance with ASTM D 792 using a sample molded in accordance with ASTM D 4895.

[0086] The above PTFE preferably has an average primary particle diameter of 350 nm or less, more preferably 330 nm or less, still more preferably 320 nm or less, even more preferably 300 nm or less, even more preferably 280 nm or less, particularly preferably 250 nm or less, and preferably 100 nm or more, more preferably 150 nm or more, still more preferably 170 nm or more, and particularly preferably 200 nm or more, in terms of high molecular weight and improved adhesiveness and flexibility of electrodes and the like. The above average primary particle diameter is measured by the following method. The PTFE aqueous dispersion is diluted with water until the solid content concentration becomes 0.15 mass%. The transmittance of the 550 nm projection light per unit length of the obtained diluted latex and the number-average particle diameter determined by measuring the orientation with a transmission electron micrograph are measured to create a calibration curve. Using this calibration curve, the number-average particle diameter is determined from the actually measured transmittance of the 550 nm projection light of each sample, and this is taken as the average primary particle diameter.

[0087] The above PTFE may have an average aspect ratio of 2.0 or less, preferably 1.8 or less, more preferably 1.7 or less, still more preferably 1.6 or less, even more preferably 1.5 or less, even more preferably 1.4 or less, even more preferably 1.3 or less, particularly preferably 1.2 or less, and most preferably 1.1 or less, in terms of excellent handleability. The above average aspect ratio may also be 1.0 or more. The above average aspect ratio is determined by observing PTFE powder or an aqueous PTFE dispersion diluted to a solid content concentration of about 1% by mass with a scanning electron microscope (SEM), performing image processing on 200 or more randomly extracted particles, and calculating the average of the ratios of the major axis to the minor axis.

[0088] The above PTFE preferably has non-melt secondary processability. The non-melt secondary processability means the property that the melt flow rate cannot be measured at a temperature higher than the melting point in accordance with ASTM D-1238 and D-2116, in other words, the property that it does not easily flow even in the melting temperature range.

[0089] The above PTFE may be a homopolymer of tetrafluoroethylene (TFE), or a modified PTFE containing a polymerization unit based on TFE (TFE unit) and a polymerization unit based on a modified monomer (hereinafter also referred to as "modified monomer unit"). The above modified PTFE may contain 99.0% by mass or more of TFE units and 1.0% by mass or less of modified monomer units. Also, the above modified PTFE may consist only of TFE units and modified monomer units. As the above PTFE, the modified PTFE is preferred in terms of improving the adhesion and flexibility of electrodes and the like. The TFE homopolymer is preferred in terms of improving handleability.

[0090] The above-mentioned modified PTFE preferably has a content of the modified monomer unit in the range of 0.00001 to 1.0% by mass based on all the polymerization units in terms of improving stretchability, adhesion, and flexibility such as that of electrodes. As the lower limit of the content of the modified monomer unit, 0.0001% by mass is more preferable, 0.001% by mass is further preferable, 0.005% by mass is even more preferable, and 0.010% by mass is particularly preferable. As the upper limit of the content of the modified monomer unit, 0.90% by mass is preferable, 0.80% by mass is more preferable, 0.50% by mass is more preferable, 0.40% by mass is further preferable, 0.30% by mass is even more preferable, 0.20% by mass is even more preferable, 0.15% by mass is even more preferable, 0.10% by mass is even more preferable, 0.08% by mass is even more preferable, 0.05% by mass is particularly preferable, and 0.03% by mass is most preferable. In this specification, the above-mentioned modified monomer unit means a part of the molecular structure of PTFE and is a part derived from the modified monomer.

[0091] The content of each of the above-mentioned polymerization units can be calculated by appropriately combining NMR, FT-IR, elemental analysis, and X-ray fluorescence analysis according to the type of monomer.

[0092] The above-mentioned modified monomer is not particularly limited as long as it can copolymerize with TFE. For example, perfluoroolefins such as hexafluoropropylene [HFP]; hydrogen-containing fluoroolefins such as trifluoroethylene and vinylidene fluoride [VDF]; perhaloolefins such as chlorotrifluoroethylene; perfluorovinyl ether; perfluoroallyl ether; (perfluoroalkyl)ethylene, ethylene, etc. may be mentioned. Also, the modified monomer used may be one kind or a plurality of kinds.

[0093] The above-mentioned perfluorovinyl ether is not particularly limited. For example, the following general formula (A): CF2=CF-ORf (A) (In the formula, Rf represents a perfluoro organic group.) Examples thereof include perfluoro unsaturated compounds represented by the formula. In the present specification, the above-mentioned "perfluoro organic group" means an organic group in which all hydrogen atoms bonded to carbon atoms are substituted with fluorine atoms. The above-mentioned perfluoro organic group may have an ether oxygen.

[0094] Examples of the above-mentioned perfluorovinyl ether include, for example, in the above general formula (A), perfluoro(alkyl vinyl ether) [PAVE] in which Rf is a perfluoroalkyl group having 1 to 10 carbon atoms. The number of carbon atoms of the above-mentioned perfluoroalkyl group is preferably 1 to 5.

[0095] Examples of the perfluoroalkyl group in the above PAVE include a perfluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluorobutyl group, a perfluoropentyl group, a perfluorohexyl group, and the like.

[0096] Examples of the above-mentioned perfluorovinyl ether further include, in the above general formula (A), those in which Rf is a perfluoro(alkoxyalkyl) group having 4 to 9 carbon atoms, and those in which Rf is the following formula:

[0097]

Chemical formula

[0098] (In the formula, m represents an integer of 0 or 1 to 4.) And those in which Rf is the following formula:

[0099]

Chemical formula

[0100] (In the formula, n represents an integer of 1 to 4.) And the like.

[0101] (Perfluoroalkyl)ethylene (PFAE) is not particularly limited, and examples thereof include (perfluorobutyl)ethylene (PFBE), (perfluorohexyl)ethylene, and the like.

[0102] Examples of the perfluoroallyl ether include, for example, the general formula (B): CF2=CF-CF2-ORf 1 (B) (In the formula, Rf 1 represents a perfluoro organic group.) Fluoromonomers represented by the formula are included.

[0103] The above Rf 1 is preferably a perfluoroalkyl group having 1 to 10 carbon atoms or a perfluoroalkoxyalkyl group having 1 to 10 carbon atoms. As the above perfluoroallyl ether, at least one selected from the group consisting of CF2=CF-CF2-O-CF3, CF2=CF-CF2-O-C2F5, CF2=CF-CF2-O-C3F7, and CF2=CF-CF2-O-C4F9 is preferable, at least one selected from the group consisting of CF2=CF-CF2-O-C2F5, CF2=CF-CF2-O-C3F7, and CF2=CF-CF2-O-C4F9 is more preferable, and CF2=CF-CF2-O-CF2CF2CF3 is even more preferable.

[0104] As the above modified monomer, at least one selected from the group consisting of PAVE and HFP is preferable in terms of improving stretchability, adhesion, and flexibility of electrodes and the like, and at least one selected from the group consisting of perfluoro(methyl vinyl ether) (PMVE) and HFP is more preferable.

[0105] As the above other modified monomer, at least one selected from the group consisting of VDF, HFP, CTFE, and PAVE is preferable in terms of forming a composite sheet having excellent strength, and at least one selected from the group consisting of VDF, HFP, and CTFE is more preferable. In terms of improving heat resistance, it is one of the preferred embodiments that the above PTFE contains TFE units, VDF units and HFP units, and the total amount of VDF units and HFP units is 1.0% by mass or less based on all polymerization units.

[0106] In terms of excellent handleability, the above PTFE preferably has a core-shell structure. Examples of PTFE having a core-shell structure include modified PTFE containing a core of high molecular weight PTFE and a shell of lower molecular weight PTFE or modified PTFE in the particles. Examples of such modified PTFE include PTFE described in JP-T-2005-527652.

[0107] In terms of being able to form a composite sheet with excellent strength, the endothermic peak temperature of the above PTFE is preferably 320 °C or higher, more preferably 325 °C or higher, still more preferably 330 °C or higher, still more preferably 335 °C or higher, still more preferably 340 °C or higher, still more preferably 342 °C or higher, and particularly preferably 344 °C or higher. The above endothermic peak temperature is also preferably 350 °C or lower. The above endothermic peak temperature is the temperature corresponding to the minimum point in the melting heat curve obtained by performing differential scanning calorimetry [DSC] at a heating rate of 10 °C / min for a fluororesin having no history of heating to a temperature of 300 °C or higher. When there are two or more minimum points in one melting peak, each is taken as the endothermic peak temperature.

[0108] In terms of being able to form a composite sheet with excellent strength, when the above PTFE is heated at a rate of 10 °C / min using a differential scanning calorimeter [DSC], one or more endothermic peaks appear in the range of 333 to 347 °C, and the heat of fusion in the range of 290 to 350 °C calculated from the above melting heat curve is preferably 62 mJ / mg or more.

[0109] In terms of being able to form a composite sheet with excellent strength, the number average molecular weight (Mn) of the above PTFE is preferably 3.0×10 6 or more, and 3.2×10 6More preferably, it is as described above, 3.5×10 6 Even more preferably, it is as described above, 3.7×10 6 Even more preferably, it is as described above, 4.0×10 6 Particularly preferably, it is as described above. The number average molecular weight is also preferably 7.0×10 6 or less, more preferably 6.5×10 6 or less, even more preferably 6.0×10 6 or less, even more preferably 5.5×10 6 or less, even more preferably 5.0×10 6 or less. Particularly preferably, it is as described above. The number average molecular weight is the molecular weight determined according to the method described in the following literature from the heat of crystallization estimated by performing a temperature drop measurement with a differential scanning calorimeter (DSC) after melting the fluororesin. The measurement is performed 5 times, and the average value of 3 values excluding the maximum value and the minimum value is adopted. Literature: Suwa, T.; Takehisa, M.; Machi, S., J. Appl. Polym. Sci. vol. 17, pp. 3253 (1973).

[0110] Preferably, the above PTFE substantially does not contain a fluorine-containing compound having a molecular weight of 1000 or less. Substantially not containing the above fluorine-containing compound means that the amount of the above fluorine-containing compound is 25 mass ppb or less with respect to the above PTFE. More preferably, the amount of the above fluorine-containing compound is less than 25 mass ppb, even more preferably 10 mass ppb or less, even more preferably 5 mass ppb or less, even more preferably 3 mass ppb or less, and particularly preferably 1 mass ppb or less. The lower limit is not particularly limited and may be an amount less than the detection limit.

[0111] The amount of the above fluorine-containing compound having a molecular weight of 1000 or less is measured by the following method. Weigh 1 g of the sample, add 10 g (12.6 ml) of methanol, perform ultrasonic treatment for 60 minutes to obtain an extract. Appropriately concentrate the obtained extract by nitrogen purging, and measure the fluorine-containing compound in the concentrated extract by LC / MS / MS. Extract the molecular weight information from the obtained LC / MS spectrum and confirm the match with the structural formula of the candidate fluorine-containing compound. Prepare aqueous solutions of the standard substance with a content of 5 levels or more, perform LC / MS analysis on the aqueous solutions of each content, plot the relationship between the content and the area of the peak corresponding to the content, and draw a calibration curve. Using the above calibration curve, convert the area of the peak in the LC / MS chromatogram of the fluorine-containing compound in the extract to the content of the fluorine-containing compound. Note that the detection limit in this measurement method is 10 mass ppb.

[0112] The amount of the fluorine-containing compound with a molecular weight of 1000 or less can also be measured by the following method. Weigh 1 g of the sample, add 10 g (12.6 ml) of methanol, perform ultrasonic treatment at 60 °C for 2 hours, let it stand at room temperature, remove the solid content, and obtain an extract. Appropriately concentrate the obtained extract by nitrogen purging, and measure the fluorine-containing compound in the concentrated extract by LC / MS / MS. Extract the molecular weight information from the obtained LC / MS spectrum and confirm the match with the structural formula of the candidate fluorine-containing compound. Prepare 5 levels of methanol standard solutions of fluorine-containing compounds with known concentrations, perform measurements using a liquid chromatograph mass spectrometer, and use linear approximation from the methanol standard solution concentration and the integral value of the peak in each concentration range to create a calibration curve. Measure the content of the fluorine-containing compound contained in the extract from the above calibration curve and convert the content of the fluorine-containing compound contained in the sample. Note that the detection limit in this measurement method is 1 mass ppb.

[0113] Examples of the fluorine-containing compound with a molecular weight of 1000 or less include fluorine-containing compounds having a hydrophilic group with a molecular weight of 1000 g / mol or less. The molecular weight of the above fluorine-containing compound is preferably 800 or less, and more preferably 500 or less. In the polymer particles obtained by polymerization carried out in the presence of a fluorine-containing surfactant, in addition to PTFE, it is normal for the fluorine-containing surfactant to be contained. In this specification, the fluorine-containing surfactant is the one used during polymerization. The fluorine-containing compound having a molecular weight of 1000 or less may be a compound that is not added during polymerization, for example, a compound that is by-produced during the polymerization. In addition, when the fluorine-containing compound having a molecular weight of 1000 or less contains an anionic part and a cationic part, it means a fluorine-containing compound in which the molecular weight of the anionic part is 1000 or less. PTFE is not included in the fluorine-containing compound having a molecular weight of 1000 or less.

[0114] Examples of the hydrophilic group may be, for example, -COOM, -SO2M, or -SO3M, -COOM, -SO3M (in each formula, M is H, a metal atom, NR 1 4, imidazolium which may have a substituent, pyridinium which may have a substituent or phosphonium which may have a substituent, and R 1 is H or an organic group.). Examples of such anionic groups are included.

[0115] As the fluorine-containing surfactant, a surfactant containing fluorine with a molecular weight of 1000 or less in the anionic part (anionic fluorine-containing surfactant) can also be used. The above "anionic part" means the part excluding the cation of the fluorine-containing surfactant. For example, in the case of F(CF2) n1 COOM, it is the part of "F(CF2) n1 COO". As the anionic fluorine-containing surfactant, the following general formula (N 0 ): X n0 -Rf n0 -Y 0 (N 0 ) (In the formula, X n0 is H, Cl or and F. Rf n0is an alkylene group having 3 to 20 carbon atoms, which is linear, branched or cyclic, and in which some or all of the H are substituted by F. The alkylene group may contain one or more ether bonds, and some of the H may be substituted by Cl. Y 0 is an anionic group. Compounds represented by ) are exemplified. Y 0 The anionic group of may be -COOM, -SO2M, or -SO3M, and may be -COOM or -SO3M. M is H, a metal atom, NR 1 4, an imidazolium which may have a substituent, a pyridinium which may have a substituent, or a phosphonium which may have a substituent, and R 1 is H or an organic group. Examples of the metal atom include alkali metals (Group 1), alkaline earth metals (Group 2), etc., and for example, Na, K or Li. R 1 may be H or an organic group of C 1-10 and may be H or an organic group of C 1-4 and may be H or an organic group of C 1-4 and may be an alkyl group of. M may be H, a metal atom or NR 1 4, and may be H, an alkali metal (Group 1), an alkaline earth metal (Group 2) or NR 1 4, and may be H, Na, K, Li or NH4. The above Rf n0 may be one in which 50% or more of H is substituted by fluorine.

[0116] The above fluorine-containing surfactant may be one kind of fluorine-containing surfactant, or may be a mixture containing two or more kinds of fluorine-containing surfactants.

[0117] Examples of the above fluorine-containing surfactant include compounds represented by the following formula. The fluorine-containing surfactant may be a mixture of these compounds. F(CF2)7COOM, F(CF2)5COOM, H(CF2)6COOM, H(CF2)7COOM, CF3O(CF2)3OCHFCF2COOM, C3F7OCF(CF3)CF2OCF(CF3)COOM, CF3CF2CF2OCF(CF3)COOM, CF3CF2OCF2CF2OCF2COOM, C2F5OCF(CF3)CF2OCF(CF3)COOM, CF3OCF(CF3)CF2OCF(CF3)COOM, CF2ClCF2CF2OCF(CF3)CF2OCF2COOM, CF2ClCF2CF2OCF2CF(CF3)OCF2COOM, CF2ClCF(CF3)OCF(CF3)CF2OCF2COOM, CF2ClCF(CF3)OCF2CF(CF3)OCF2COOM, and, [Chemical formula] (In each formula, M is H, a metal atom, NR 1 4, imidazolium which may have a substituent, pyridinium which may have a substituent or phosphonium which may have a substituent. R 1 is H or an organic group.). It is preferable that the above PTFE does not substantially contain any of the fluorine-containing compounds represented by the above formulae.

[0118] In each of the above formulae, M may be H, a metal atom or NR 1 4, and may be H, an alkali metal (Group 1), an alkaline earth metal (Group 2) or NR 1 4, and may be H, Na, K, Li or NH4. R 1 may be H or an organic group of C 1-10 and may be H or an organic group of C 1-4 and may be H or an alkyl group of C 1-4 .

[0119] When the above PTFE substantially contains none of the fluorine-containing compounds represented by the above formula, generation of gas and deterioration of battery characteristics can be suppressed, and sheet strength can also be improved. Substantially containing none of the fluorine-containing compounds represented by the above formula means that the amount of the fluorine-containing compound is 25 mass ppb or less with respect to the above PTFE. The amount of the fluorine-containing compound is preferably less than 25 mass ppb, more preferably 10 mass ppb or less, still more preferably 5 mass ppb or less, even more preferably 3 mass ppb or less, and particularly preferably 1 mass ppb or less. The lower limit is not particularly limited and may be an amount less than the detection limit.

[0120] The above PTFE preferably substantially contains no fluorine-containing compound represented by the following general formula: [C n-1 F 2n-1 COO - M + (In the formula, n is an integer of 9 to 14, preferably an integer of 9 to 12, and M + represents a cation.) Substantially containing no fluorine-containing compound represented by this can also suppress generation of gas and deterioration of battery characteristics, and can also improve sheet strength. The cation M + constituting M in the above formula is the same as the above-described M. Substantially containing none of the fluorine-containing compounds represented by the above formula means that the amount of the fluorine-containing compound is 25 mass ppb or less with respect to the above PTFE. The amount of the fluorine-containing compound is preferably less than 25 mass ppb, more preferably 10 mass ppb or less, still more preferably 5 mass ppb or less, even more preferably 3 mass ppb or less, and particularly preferably 1 mass ppb or less. The lower limit is not particularly limited and may be an amount less than the detection limit.

[0121] Although the embodiments have been described above, it will be understood that various changes in form and details are possible without departing from the spirit and scope of the claims.

Example

[0122] Next, the present disclosure will be described with reference to experimental examples, but the present disclosure is not limited to such examples only.

[0123] <Standard Specific Gravity (SSG)> Using a sample molded in accordance with ASTM D4895 89, it was measured by the water displacement method in accordance with ASTM D 792.

[0124] <RR100 Extrusion Pressure (Extrusion Pressure at Reduction Ratio 100)> 50 g of PTFE powder and 10.25 g of hydrocarbon oil (trade name: Isopar E, manufactured by ExxonMobil) as an extrusion aid were mixed in a polyethylene container for 3 minutes. At room temperature (25 ± 2 °C), the above mixture was filled into the cylinder of an extruder, and a load of 0.47 MPa was applied to the piston inserted into the cylinder and held for 1 minute. Next, it was extruded from the orifice at a ram speed of 51 cm / min. The ratio of the cross-sectional area of the cylinder to the cross-sectional area of the orifice was 100. In the latter half of the extrusion operation, the value obtained by dividing the load (N) when the pressure reached an equilibrium state by the cross-sectional area of the cylinder was taken as the extrusion pressure (MPa).

[0125] <Elongation Test> The elongation test was carried out according to the method described in JP-A-2002-201217 as follows. The beads obtained by the above paste extrusion were heated at 230 °C for 30 minutes to remove the lubricant from the beads. Next, the beads (extruded bodies) were cut to an appropriate length, and each end was fixed to a clamp so that the clamp interval was 1.5 inches (38 mm), and heated to 300 °C in an air circulation furnace. Then, the clamps were separated at a desired speed (stretch speed) until the separation distance corresponded to the desired stretch (total stretch), and a stretch test was carried out. This stretch method essentially followed the method disclosed in U.S. Patent No. 4,576,869, except that the extrusion speed (51 cm / min instead of 84 cm / min) was different. "Stretch" means an increase in length by stretching, and is usually expressed as a ratio to the original length. In the stretch method, the stretch speed was 1000% / second, and the above total stretch was 2400%. In the above stretch test, those that did not break during stretching were considered stretchable, and those that broke during stretching were considered non-stretchable.

[0126] <Apparent density> Measured in accordance with JIS K6892.

[0127] <Powder particle size> Determined by the laser diffraction method. Using the HELOS&ROD OS system (trade name, manufactured by SYMPATEC), it was carried out dry. The powder to be measured dispersed by compressed air with a dispersion pressure of 2 bar was measured by the measurement sensor part sensing the shadow of the powder to be measured projected by the laser, and the particle size distribution of the powder to be measured was calculated, and the value of the average particle size (50% integrated particle size) d50 was determined on a volume basis. The powder particle size was assumed to be equal to the particle size corresponding to 50% of the particle size distribution integration.

[0128] <Moisture content> The mass of about 20 g of PTFE powder before and after heating at 150 °C for 2 hours was measured and calculated according to the following formula. The sample was taken 3 times, calculated respectively, and the average was obtained, and the average value was adopted. Moisture content (mass%) = [(mass of PTFE powder before heating (g)) - (mass of PTFE powder after heating (g))] / (mass of PTFE powder before heating (g)) × 100

[0129] <Agglomeration property of powder> 60 g of the stored PTFE powder was taken out from the container, screened through a mesh (aperture 1.54 mm), and the mass of the agglomerates remaining on the sieve was measured. The above operation was repeated 10 times, and the average value of the mass of the agglomerates remaining on the sieve was determined. Based on the value of the average value (g) / 60 (g) × 100 (mass %), the agglomeration property of the powder was evaluated. The smaller the value, the less likely the powder is to agglomerate and the better it is.

[0130] <Preparation of positive electrode mixture> As the positive electrode active material, Li(Ni 0.6 Mn 0.2 Co 0.2 )O2 (NMC622), carbon black as the conductive assistant, and PTFE powder as the binder were weighed so that the mass ratio of the positive electrode active material: binder: conductive assistant = 95:2:3. These materials were put into a blender (manufactured by Osaka Chemical Co., Ltd.: WB-1) and stirred at 25,000 rpm for 60 seconds to obtain a positive electrode mixture.

[0131] <Ease of binding> A sieve with an aperture of 2.0 mm, a sieve with an aperture of 0.15 mm, and a bottom-receiving container were stacked vertically in a shaker, and the above positive electrode mixture was put into the upper sieve. After operating at a speed of 50 rpm for 1 minute, the mass of the mixture that had fallen onto the bottom-receiving container was measured. Based on the desorption rate calculated from the following formula, the ease of binding (the ease of the mixture to aggregate) of the mixture was evaluated. Desorption rate = (W2 / W1) × 100 (%) (In the formula, W1 represents the total mass (g) of the mixture before the test, and W2 represents the mass (g) of the mixture that has fallen through the sieve.) Excellent: Desorption rate less than 1% Good: Desorption rate 1% or more and less than 2% Fair: Desorption rate 2% or more and less than 3% Poor: Desorption rate 3% or more

[0132] Experimental Example 1 A plastic container (material: polypropylene, no plasticizer (content in polypropylene is 0% by mass), surface roughness of the inner wall is 0.23 μm) with a taper angle of 3.0° and a difference of 30 mm between the inner diameter of the upper surface and the inner diameter of the lower surface, having an inner volume of 60 L, was filled with 15 kg of PTFE powder and stored in an atmosphere of 25°C for six months. The caking property of the stored PTFE powder was 0.4% by mass, and the moisture content was 0.002% by mass. The positive electrode binder mixture was prepared by the above method, and the ease of binding was evaluated. The desorption rate was 0.4% by mass, and the ease of binding was excellent. The PTFE powder used was the PTFE powder described in Example 1 of International Publication No. 2023 / 054709, with a standard specific gravity (SSG) of 2.159, an RR100 extrusion pressure of 15.1 MPa, being extensible, a powder particle size of 540 μm, an apparent density of 0.48 g / ml, and a moisture content of 0.002% by mass.

[0133] Experimental Example 2 A container having the same shape as that in Experimental Example 1, equipped with a clamp for fixing the lid attached to the opening and the container. The PTFE powder filled in the container was the PTFE powder described in Example 2 of International Publication No. 2023 / 054707, with a standard specific gravity (SSG) of 2.145, an RR100 extrusion pressure of 17.4 MPa, being extensible, a powder particle size of 540 μm, an apparent density of 0.43 g / ml, and a moisture content of 0.000% by mass. Except for this, it was stored in an atmosphere of 25°C for six months in the same manner as Experimental Example 1. The caking property of the stored PTFE powder was 0.3% by mass, and the moisture content was 0.001% by mass. As a result of evaluating the ease of binding of the positive electrode binder mixture, the desorption rate was 0.5% by mass, and the ease of binding was excellent.

[0134] Experimental Example 3 It had a shape in which the step provided on the lid and the protrusion provided on the container body meshed with each other. Except for using silica gel as a desiccant in the container, it was stored in an atmosphere of 10°C for six months in the same manner as Experimental Example 2. The caking property of the stored PTFE powder was 0.2% by mass, and the moisture content was 0.000% by mass. As a result of evaluating the ease of binding of the positive electrode binder mixture, the desorption rate was 0.5% by mass, and the ease of binding was excellent.

[0135] Experimental Example 4 The PTFE powder filled in the container is the PTFE powder described in Example 18 of International Publication No. 2023 / 054723. It was stored for six months in an atmosphere of 25°C in the same manner as in Experimental Example 2, except that the standard specific gravity (SSG) was 2.170, the extrusion pressure of RR100 was 5.6 MPa, it was not stretchable, the powder particle size was 540 μm, the apparent density was 0.48 g / ml, and the moisture content was 0.001% by mass. The caking property of the stored PTFE powder was 0.1% by mass, and the moisture content was 0.002% by mass. As a result of evaluating the ease of binding of the positive electrode binder mixture, the desorption rate was 0.8% by mass, and the ease of binding was excellent.

[0136] Experimental Example 5 Except that 5 kg of PTFE powder was put into a plastic container (material: polypropylene, no plasticizer (content with respect to polypropylene is 0% by mass), surface roughness of the inner wall is 0.23 μm) with an internal volume of 30 L, a forward taper angle of 0°, and a difference between the inner diameter of the upper surface and the inner diameter of the lower surface of 0 mm, it was stored for six months in an atmosphere of 25°C in the same manner as in Experimental Example 1. The caking property of the stored PTFE powder was 2.5% by mass, and the moisture content was 0.005% by mass. As a result of evaluating the ease of binding of the positive electrode binder mixture, the desorption rate was 2.1% by mass, and the ease of binding was fair.

[0137] Experimental Example 6 The PTFE aqueous dispersion obtained by Production Example 1 of International Publication No. 2023 / 054713 was diluted to a solid content concentration of 8.5% by mass, the liquid temperature was adjusted to 10°C, nitric acid was added, and high-speed stirring was performed in the container to cause coagulation, followed by drying at 210°C to obtain PTFE powder. The obtained PTFE powder had a standard specific gravity (SSG) of 2.158, an extrusion pressure of RR100 of 16.3 MPa, was stretchable, a powder particle size of 145 μm, an apparent density of 0.35 g / ml, and a moisture content of 0.002% by mass. Using the obtained PTFE powder, it was stored for six months in an atmosphere of 25°C in the same manner as in Experimental Example 5. The caking property of the stored PTFE powder was 1.5% by mass, and the moisture content was 0.005% by mass. As a result of evaluating the ease of binding of the positive electrode binder mixture, the desorption rate was 1.3% by mass, and the ease of binding was good.

[0138] Experimental Example 7 Using a plastic container (material: polypropylene, no plasticizer (content in polypropylene is 0% by mass), surface roughness of the inner wall is 0.23 μm) with a taper angle of 0°, that is, the difference between the inner diameter of the upper surface and the inner diameter of the lower surface is 0 mm, it was stored in the same manner as in Experimental Example 1. The degree of agglomeration of the stored PTFE powder was 5.6% by mass. The positive electrode mixture was prepared by the above method, and the ease of binding was evaluated. The desorption rate was 3.6% by mass, and the ease of binding was poor.

Explanation of Signs

[0139] 1: Container 2: Main body 2a: Inner wall 2b: Outer wall 2c: Opening 2d: Projection 2e: Step 3: Lid 3a: Step 3b: Projection 4: Clamp 4a: Mounting part A: Taper angle

Claims

1. A container for filling polytetrafluoroethylene, comprising: A container whose inner side wall is cylindrical and tapered either forward or reverse.

2. 2. The container according to claim 1, wherein the polytetrafluoroethylene has an extrusion pressure of 5 MPa or more at a reduction ratio of 100 and / or is stretchable.

3. 3. The container according to claim 1, wherein the polytetrafluoroethylene has an extrusion pressure of 5 MPa or more at a reduction ratio of 100 and is stretchable.

4. 3. The container according to claim 1, wherein the polytetrafluoroethylene has an extrusion pressure of 5 to 20 MPa at a reduction ratio of 100.

5. 3. The container according to claim 1, wherein the polytetrafluoroethylene is used as a binder for an electrochemical device.

6. 3. The container according to claim 1, wherein the difference between the inner diameter of the upper surface and the inner diameter of the lower surface is 5 to 100 mm.

7. 3. The container according to claim 1, wherein the taper angle is 0.5 to 10°.

8. 3. The container according to claim 1 or 2, wherein the material is polypropylene substantially free of plasticizer.

9. 3. The container according to claim 1, wherein the surface roughness of the inner wall is 1.00 μm or less.

10. A body having an opening; A lid attached to the opening; 3. The container according to claim 1 or 2, further comprising a clamp for fixing the lid.

11. The container of claim 10, wherein the lid is attached to the opening with a step on the lid engaging with a protrusion on the main body and / or with a protrusion on the lid engaging with a step on the main body.

12. 3. The container according to claim 1, wherein the polytetrafluoroethylene has a moisture content of 0.050% by mass or less.

13. 3. The container according to claim 1, wherein the apparent density of the polytetrafluoroethylene is 0.40 to 0.60 g / ml.

14. 3. The container according to claim 1, wherein the apparent density of the polytetrafluoroethylene is 0.43 to 0.60 g / ml.

15. 3. The container according to claim 1, wherein the powder particle size of the polytetrafluoroethylene is 300 to 700 μm.

16. 3. The container according to claim 1, wherein the powder particle size of the polytetrafluoroethylene is 500 to 700 μm.

17. 3. The container according to claim 1, wherein the standard specific gravity of said polytetrafluoroethylene is 2.200 or less.

18. 3. The container according to claim 1, wherein the standard specific gravity of the polytetrafluoroethylene is 2.130 to 2.

170.

19. 3. The container according to claim 1, wherein the polytetrafluoroethylene has an apparent density of 0.43 to 0.60 g / ml, a powder particle size of 500 to 700 μm, and a standard specific gravity of 2.130 to 2.

170.

20. 3. The container according to claim 1, wherein the polytetrafluoroethylene is a homopolymer of tetrafluoroethylene or a modified polytetrafluoroethylene containing polymerization units based on tetrafluoroethylene and polymerization units based on a modified monomer.

21. 21. The container according to claim 20, wherein the modifying monomer is at least one selected from the group consisting of perfluoro(methyl vinyl ether) and hexafluoropropylene.

22. 3. The container according to claim 1 or 2, which is filled with polytetrafluoroethylene.

23. 3. The container according to claim 1 or 2, wherein the container comprises a moisture absorbent.

24. 3. A method for storing polytetrafluoroethylene, comprising filling the container according to claim 1 or 2 with the polytetrafluoroethylene and storing the same.

25. A container for filling polytetrafluoroethylene, comprising: A container in which the mass of the polytetrafluoroethylene filled therein is 10 kg or less.

26. 26. The container according to claim 25, wherein the mass of the polytetrafluoroethylene to be filled is 5 kg or less.

27. 27. The container according to claim 25 or 26, wherein the powder particle size of the polytetrafluoroethylene is 100 μm or more and less than 600 μm.

28. 27. The container according to claim 25 or 26, wherein the apparent density of the polytetrafluoroethylene is 0.35 to 0.48 g / ml.

29. 27. The container according to claim 25 or 26, wherein the polytetrafluoroethylene has a moisture content of 0.050% by mass or less.

30. 27. The container according to claim 25 or 26, wherein the polytetrafluoroethylene has a moisture content of 0.005% by mass or less.

31. 27. The container according to claim 25 or 26, wherein the standard specific gravity of the polytetrafluoroethylene is 2.130 to 2.

170.

32. The container according to claim 25 or 26, wherein the polytetrafluoroethylene has a moisture content of 0.005% by mass or less, an apparent density of 0.35 to 0.48 g / ml, a powder particle size of 100 μm or more and less than 600 μm, and a standard specific gravity of 2.130 to 2.

170.

33. 27. The container according to claim 25 or 26, wherein the polytetrafluoroethylene has a powder particle size of 100 μm or more and less than 300 μm and / or an apparent density of 0.35 g / ml or more and less than 0.40 g / ml.

34. 27. The container according to claim 25 or 26, which is filled with polytetrafluoroethylene.

Images